Are you using the vanagon dipstick (behind the license) or AAZ dipstick (side of motor). I didn't think the latter would work with the vanagaon diesel oil pan . . .
VW never put AAZ motors in vanagons, and so there's a little ambiguity re oil quantity. It will take a little more than a stock vanagon, on account of the turbo. 4.5 quarts should be right.
The stock vanagon diesel dipstick is not very accurate . . .